package mylib.archive.y2012.m08.SNSS_R4;

import mylib.dir.FastInputReader;
import mylib.dir.MathUtils;

import java.io.PrintWriter;

public class TaskF {

    public void solve(int testNumber, FastInputReader in, PrintWriter out) {
        int m = in.nextInt();
        int f = in.nextInt();
        int a = in.nextInt();
        int b = in.nextInt();
        out.print(MathUtils.binomial(20)[m][a] * MathUtils.binomial(20)[f][b]);
    }
}
